Biochemical Markers - Detecting Osteoporosis: Osteoporosis
Content provided by the Faculty of the Harvard Medical School
Biochemical markers
Several companies have developed blood and urine tests that indicate the rate at which bone is being formed and destroyed by measuring the markers of bone turnover. While these tests are sometimes used, the information they can provide is limited, and they can't tell you if you are at risk of breaking a bone.
Some of these tests measure collagen cross-links — proteins contained in the structural framework of bone, which are released during bone resorption. Others measure alkaline phosphatase and osteocalcin, proteins that are instrumental to bone formation. These tests can indicate high bone turnover, which can be a sign of rapid bone loss. However, they cannot indicate bone mass any more than measurements of metabolic rate can indicate a person's weight. Like metabolism, bone turnover varies from person to person and from time to time. Thus, a turnover rate that may point to bone loss in one person may represent the status quo for another.
These tests are sometimes used to provide an early indication of whether someone is responding well to treatment for bone loss. A urine test revealing that bone turnover has slowed following treatment can be seen as a sign that therapy is having an effect. But it's not clear if this translates into slower bone loss or improvement in bone density. Conversely, test results showing that the rate of bone turnover has remained the same or increased may indicate that the treatment is ineffective or that the patient is not taking the medication.
Don't give up on therapyWhile bone mineral density (BMD) tests are often used to monitor how a patient is responding to treatment, one study concluded that an initial loss of BMD after beginning drug therapy may not be cause for concern. The study, published in 2000 in the Journal of the American Medical Association, indicated that some patients lose BMD after their first year of therapy, only to gain it during their second year. The study's message was that patients should stick with treatment even if an initial BMD test shows less than stellar results. Because losses are sometimes the result of patients not taking their medications, a poor showing should prompt doctors to talk with their patients. But the losses may also reflect individual variations in bone density, imperfections in testing methods, or random errors. |
But markers can't reveal fracture risk, and they seem to correlate only dimly with changes in bone mass in an individual. Currently, they can't routinely provide you with enough information to make a decision about whether to undertake or forgo preventive treatment, but they may be helpful under certain circumstances when bone turnover needs to be assessed.
| Last updated: | January 23, 2007 |
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Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.
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